US2397301A - Chemical process - Google Patents

Description

Patented Mar. 26, 1946 CHEMICAL PROCESS Hans c. Vesterdal, Elizabeth, N. 1., mum: to

Standard Oil Development Company, a corporation of Delaware No Drawing. Application September 17, 1943. Serial No. 502,791

4 Claims.

This invention relates to the production oi higher molecular weight hydrocarbons from lower molecular weight hydrocarbons and, more particularly, to an improvement in the production of hydrocarbons boiling in the gasoline range from normally gaseous hydrocarbons.

It is known that normallygaseous unsaturated hydrocarbons may be converted to normally liquid hydrocarbons by treatment at elevated temperatures with or without catalysts and both with and without high superatmospheric pressure. Inparticular, it is known that propylene may be condensed into liquid hydrocarbons boiling mainly in the gasoline range by heating this olefin to a temperature between 700 and 900 F. under a pressure between 500 and 15,000 lbs/sq. in. for a short time.

One object of this invention is the conversion of gaseous hydrocarbons into high quality liquid hydrocarbons useful as motor fuels.

Another object is to effect the transformation or polymerization in an economical manner by the action of catalysts under high pressure.

Another object of this invention is to produce a high yield of low boiling hydrocarbon liquids boiling in the gasoline range and having good anti-knock rating and high blending value.-

Qther objects will be apparent from the detailed discussion which follows.

A specific embodiment of the invention comprises treating normallyigaseous olefin hydrocar- The present process is particularly directed to the production of dimers and trimers from monoolefins, particularly those oleflns whose lower polymers boil at temperatures within the approximate range of commercial motor-fuel, that is between 100 and 400 F. It has been found that the dimers and some or the trimers of propylene,

for example, boil within this range and furthermore that these compounds have unusually high antiknock characteristics.

The main feature or the present invention which stands asan improvement in the art 01' polymerizing gaseous olefins by catalysts and, more particularly, by oxide catalysts exemplified by chromium oxide deposited on alumina con sists in the use of regulated amounts of water or steam in the gas mixture undergoing polymerization. When passing a dry gas mixture containing about 95% propylene over a catalyst composed of chromium oxide deposited on alumina at a temperature between 775 and 785 F. and at an average pressure of about 2200 lbs/sq. in., the yield of liquid products was 65.5 weight percent based on total feed and 70.2 weight percent based on propylene consumed. Upon adding 0.25 mol percent of steam to the feed, the corresponding yields were 76.4 and 84.2 weight percent,

respectively, and on adding 1.4 mol percent steam to the feed, the corresponding yields were 80.5 and 89.0%. respectively. At a somewhat higher pressure, 2800 lbs/sq. in., the yields were 88.2 and 94.? weight percent on total feed and olefin consumed, respectively, when adding 1.4 mol percent steam to the feed.

Similar improvements in yields on addition of steam were also noticed when operating without catalyst. The data thus obtained are summarized in the following table: I

Propylene condensation 1 Feed Propylene, 95% pure I Catalyst Ohromia-slumina N0 catalyst Run N0. 768- 99 89 97 103 107 Reaction time" 70 132 134 30 144 70 70 70 Temp 785 776 780 785 785 785 775 790. Pressure 2, 200 1, 900 2, 800 2, 200 2,000 2, 200 2, 300 2, 200 IO/CrHq ratio X100 0. 25 1. 4 1. 4 0. 31 0 0. 3 2. 9 11- 8 Yield of liquid product, wt. perce 1. Based on total iced 76. 4 80. 5 88, 2 73. 7 56. 2 69. 7 73.0 00. 1 2. Based on CgH. consumed 84.2 89.0 94. 7 82.0 60. 6 74.6 78.7 75. l Gasoline cut (-400 R), 'wt. percent in liquid 01. l 50. 0 55. 0 59. 2 02. 4 59. 0 64. 8 6B. 5 Composition of gas. cut:

Oleflns 26 32 30 31 20 22 24 23 Aromatics... 7 3 5 6 l9 l0 5 l2 Naphthenes 32 33 28 33 43 87 41 33 I Parafilns --do-- 20 35 32 37 30 18 31 30 32 The polymerizing of gaseous oleflns of the yields of liquid hydrocarbons boiling in the motor present character may be brought about under fuel range.

,products is very high when operating at or above certain pressures depending on the temperature of operation. Thus, when operating without cats alyst at 775 F. a high rate of reaction starts when the pressure is raised to 2400-2600 lbs/sq. in. At 860' F. the pressure for high reaction rate is about 1200 lbs/sq. in. When operating at or above such pressures, a reaction time of less than b one minute is necessary for practically complete condensation. When using a chromia-alumina catalyst the pressure for high reaction rate is several hundred pounds per square inch lower than when no catalyst is present, provided the temperature is held between about 750 F. and 850 F. When operating without catalyst the pressures for high reaction rate at various temperatures are as follows:

Temperature, F.

Pressure for high reaction rate,

lbs/sq. lIl. .i.... 3, 100 2. 700 1, (I 1, (Hi0 In order to produce high yields of normally saturated hydrocarbons, it is preferred to hold the reaction temperature between about 775 and 800 F. and the pressure at or above the high reaction rate pressure, that is, at or above 2400 lbs/sq. in. when operating at 775 F. and 2100 lbs/sq. in. when operating at 800 F. At the same time. from 0.2 to about mol percent of steam should be added to the propylene feed. The reaction is preferably carried out in a continuous flow system and at contact times between about /2 and 180 minutes.

Higher and lower temperatures may be used, but when operating at temperatures below 750 F. the product is generally more unsaturated. At temperatures above 850 F. short contact times must be employed in order to prevent carbon formation.

' liquid hydrocarbons which comprises subjecting From the above data it will be seen that with the gas mixture applied the optimum percentage of steam is somewhat between 0.25 and 1.4 mol percent. This percentage will necessarily be varled in case of gas mixtures containing various percentages of higher oleflns and will also be in.- fluenced by the temperature and pressure found most suitable for the economical removal of olefin from diflerent cracked gas mixtures by the present process.

The reason why higher yields are obtained when small amounts or steam are added to the feed is not quite clear and it is not intended to limit the present invention by claiming the theory involved but for the sake oi! clarity it may be said that it has been found that the residual gas is more saturated when no steam is present, indicating that the propylene has been hydrogenated to form propane which is not nearly as reactive as the propylene in the condensation reaction. The nature and objects of the present invention having thus been set forth and specific examples of the same given, what is claimed as new and useful and desired to be secured by Letters Patcut is:

1. A process for the conversion oi propylene to propylene to temperatures between 775 and 800 F. and to high pressures in the presence of from 0.25 to 5 mol percent of steam and a catalyst comprising chromium oxide and alumina.

2. A process for the conversion of propylene to liquid hydrocarbons which comprises subjecting propylene to a temperature between 775 and 800 F. and a pressure between 2100 and 2400 lbs./sq. in. in the presence of from 0.25 to 5 mol percent of steam and a catalyst comprising chromium oxide and alumina.

3. A process for the conversion of propylene to liquid hydrocarbons which comprises subjecting propylene to a temperature of 775 and a pressure of 2400 lbs/sq. in. and in the presence of 0.25 to 1.4 mol percent of steam and a catalyst comprising chromium oxide and alumina for a contact time between 0.5 and 180 minutes.

4. A process for the conversion of propylene to liquid hydrocarbons which comprises subjecting propylene to a temperature of 800 F. and a pressure of 2100 lbs/sq. in. and in the presence of 0.25 to 1.4 mol percent of steam and a catalyst comprising chromium oxide and alumina for a con-' tact time between 0.5 and 180 minutes.

HANS G. VESTERDAL.